The Analytical Core provides routine and non-routine analytical service to the University of Iowa research program. The core will provide expert staff, equipment, and instrumentation in line with five Aims. Specific Aim 1 is the development of analytical and quality control/assurance standards. In close collaboration with the Synthesis Core, which is responsible for acquiring and archiving individual compound standards and preparing stock solutions, the Analytical Core will develop the mathematical methods for congener representation, analyze single congener solutions for purity assessment and quality control, and test the prepared standard solutions against certified Standard Reference Materials, including PCB calibration mixtures. Specific Aim 2 is the development of a mixture of PCB congeners for laboratory animal exposure studies. The Analytical Core will develop the mathematical methods to design the exposure mixture and test the prepared mixture against certified Standard Reference Materials. Specific Aim 3 is the analysis of environmental and laboratory samples for a suite of PCB congeners (>120). The Analytical Core will extract and analyze PCBs on a congener-specific basis. Applying the primary calibration standard developed under Aim 1, samples will be quantified by the isotope dilution method and the internal standard method. Internal Standards and .Surrogate Recovery Standards developed under Aim 1 will be used to precisely determine PCB concentrations in samples. Methods for analysis on a congener-specific basis will be assessed using performance standard injections and analysis of certified Standard Reference Materials. Some analyses will be performed on the entire suite of PCB congeners, including laboratory animals exposed to the mixture described in Aim 2 and including blood from humans and non-laboratory animals. Other samples will be analyzed for specific congeners and metabolites in support of investigators focused on congener-specific toxicology. Specific Aim 4 involves the extraction, identification, and quantification of unknown metabolites. The Analytical Core will determine purity of synthesized metabolites and associated analytical standards, then analyze for hydroxylated PCBs and other PCB metabolites. As requested by the sbrp investigators, the Analytical Core will also train personnel and assist in sampling design and implementation. Specific Aim 5 is the design and maintenance of a database system. A redundant storage architecture with automatic backup and password protection will be used to allow investigators to download data and reports produced by the Analytical Core.